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United States Patent |
5,046,585
|
Ohta
,   et al.
|
September 10, 1991
|
Upright assembly for fork lift truck
Abstract
An upright assembly for a fork lift truck is disclosed in which the
assembly comprises an outer mast of U-shaped cross-section and an inner
mast also of U-shaped cross-section that is received in the space within
the outer mast. In order to keep the overall height of the upright
assembly low, and to keep sliding resistance between the masts small, the
inner mast is supported by an inner mast roller to counter the large
forward moments and the inner mast is supported by liners to counter the
small rearward moments.
Inventors:
|
Ohta; Shuji (Kariya, JP);
Takeuchi; Toshiyuki (Kariya, JP)
|
Assignee:
|
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho (Kariya, JP)
|
Appl. No.:
|
482695 |
Filed:
|
February 21, 1990 |
Foreign Application Priority Data
| Feb 23, 1989[JP] | 1-44294 |
| Feb 23, 1989[JP] | 1-44295 |
Current U.S. Class: |
187/226; 187/238 |
Intern'l Class: |
B66B 009/20 |
Field of Search: |
187/9 E,9 R,95
|
References Cited
U.S. Patent Documents
2888300 | May., 1959 | Curtis et al. | 187/9.
|
2936047 | May., 1960 | Quayle | 187/9.
|
4307792 | Dec., 1981 | Benson et al. | 187/9.
|
4921075 | May., 1990 | Schumacher et al. | 187/9.
|
Foreign Patent Documents |
49-49548 | Dec., 1974 | JP.
| |
54-159575 | Nov., 1979 | JP.
| |
Primary Examiner: Valenza; Joseph E.
Assistant Examiner: Nguyen; Tuan N.
Attorney, Agent or Firm: Brooks Haidt Haffner & Delahunty
Claims
What is claimed is:
1. An upright assembly for a forklift truck, comprising a U-shaped
cross-sectional outer mast having an upper end and a lower end and
oriented facing a side of said truck to thereby provide an outer mast
front leg having inner and outer surfaces and an outer mast rear leg
having inner and outer surfaces, and a U-shaped cross-sectional inner mast
having an upper end and a lower end and slidably received within the
U-shape of said outer mast to thereby provide an inner mast front leg
having an outer surface cofacing said outer mast front leg inner surface
and an inner mast rear leg having an outer surface cofacing said outer
mast rear leg inner surface, an outer mast roller mounted on said upper
end of the outer mast in rolling engagement with said inner mast front leg
outer surface, a rear liner attached to said outer mast rear leg inner
surface adjacent to said outer mast upper end and in sliding engagement
with said inner mast rear leg outer surface, an inner mast roller mounted
on said lower end of the inner mast in rolling engagement with said outer
mast front leg outer surface, and a front liner attached to said inner
mast front leg outer surface adjacent to said inner mast lower end and in
sliding engagement with said outer mast front leg inner surface.
2. An upright assembly as claimed in claim 1, wherein said inner mast
roller is mounted on a roller bracket attached to said inner mast lower
end and extending forwardly of, and around said outer mast front leg so as
to be clear of engagement with said outer mast.
3. An upright assembly according to claim 2, wherein said outer mast front
leg outer surface has a longitudinal plate attached thereto adjacent to
said inner mast roller bracket and extending substantially between said
outer mast upper and lower ends, said longitudinal plate projecting
forwardly of said outer mast front leg substantially to the same extent as
said inner mast roller bracket extends forwardly of said outer mast front
leg.
4. An upright assembly as claimed in claim 1, wherein the web of said
U-shaped outer mast provides laterally facing, respectively opposite inner
and outer side surfaces of said outer mast, and the web of said U-shaped
inner mast provides laterally facing, respectively opposite inner and
outer side surfaces of said inner mast, and which further comprises a mast
side roller mounted on said outer mast inner side surface adjacent to said
outer mast upper end and in rolling engagement with said inner mast outer
side surface, and a side liner mounted on said inner mast outer side
surface adjacent to said inner mast lower end and in sliding engagement
with said outer mast inner side surface, whereby said side roller and said
side liner receive lateral force moments acting on said inner mast.
5. An upright assembly as claimed in claim 4, wherein said outer mast inner
side surface has a laterally projecting sliding surface extending
substantially between said outer mast upper and lower ends, said side
liner being in sliding contact with said outer mast sliding surface.
6. An upright assembly as claimed in claim 1, wherein the web of said
U-shaped outer mast provides laterally facing, respectively opposite inner
and outer side surfaces of said outer mast, and the web of said U-shaped
inner mast provides laterally facing, respectively opposite inner and
outer side surfaces of said inner mast, and which further comprises an
outer mast side roller mounted on said outer mast inner side surface
adjacent to said outer mast upper end and in rolling engagement with said
inner mast outer side surface, and an inner mast side roller mounted on
said inner mast outer side surface adjacent to said inner mast lower end
and in rolling engagement with said outer mast inner side surface, whereby
said inner mast and outer mast side rollers receive lateral force moments
acting on said inner mast.
7. An upright assembly for a forklift truck comprising a U-shaped
cross-sectional outer mast having an upper end and a lower end and
oriented facing a side of said truck to thereby provide an outer mast
front leg having inner and outer surfaces and an outer mast rear leg
having inner and outer surfaces, and a U-shaped cross-sectional inner mast
having an upper end and a lower end and slidably received within the
U-shape of said outer mast to thereby provide an inner mast front leg
having an outer surface cofacing said outer mast front leg inner surface
and an inner mast rear leg having an outer surface cofacing said outer
mast rear leg inner surface, an outer mast roller mounted on said upper
end of the outer mast in rolling engagement with said inner mast front leg
outer surface, a rear liner attached to said outer mast rear leg inner
surface adjacent to said outer mast upper end and in sliding engagement
with said inner mast rear leg outer surface, and an inner mast lower
roller mounted on said lower end of the inner mast adjacent to, and
projecting rearwardly of said inner mast rear leg in rolling engagement
with said outer mast rear leg inner surface.
8. An upright assembly for a forklift truck according to claim 7, wherein
the web of said U-shaped outer mast provides laterally facing,
respectively opposite inner and outer side surfaces of said outer mast,
and the web of said U-shaped inner mast provides laterally facing,
respectively opposite inner and outer side surfaces of said inner mast,
and which further comprises an inner mast lower roller bracket including a
laterally disposed roller pin on which said inner mast lower roller is
mounted, said inner mast lower roller bracket having an oblique front
side, and a vertically movable forklift apparatus having a lift mounting
bracket extending rearwardly therefrom adjacent and substantially parallel
to said web of said U-shaped inner mast, said lift mounting bracket having
a lower edge and carrying a lift roller mounted thereon adjacent to and
projecting below its said lower edge and received within said inner mast
U-shape for rolling engagement along one of said inner mast front and rear
legs, whereby said lift roller is disposed closely adjacent to said
oblique front side of said inner mast lower roller bracket when said
forklift if in a fully lowered position of its said vertical movement.
9. An upright assembly as claimed in claim 8, which further comprises a
mast side roller mounted on said outer mast inner side surface adjacent to
said outer mast upper end and in rolling engagement with said inner mast
outer side surface, and a side line mounted on said inner mast outer side
surface adjacent to said inner mast lower end and in sliding engagement
with said outer mast inner side surface, whereby said side roller and said
side liner receive lateral force moments acting on said inner mast.
10. An upright assembly as claimed in claim 9, wherein said outer mast
inner side surface has a laterally projecting sliding surface extending
substantially between said outer mast upper and lower ends, said side
liner being in sliding contact with said outer mast sliding surface.
11. An upright assembly as claimed in claim 8, which further comprises an
outer mast side roller mounted on said outer mast inner side surface
adjacent to said outer mast upper end and in rolling engagement with said
inner mast outer side surface, and an inner mast side roller mounted on
said inner mast outer side surface adjacent to said inner mast lower end
and in rolling engagement with said outer mast inner side surface, whereby
said inner mast and outer mast side rollers receive lateral force moments
acting on said inner mast.
12. An upright assembly for a forklift truck, comprising a pair of
laterally spaced apart and laterally joined U-shaped cross-sectional outer
masts each having an upper end and a lower end and oriented facing a side
of said truck to thereby provide with respect to each an outer mast front
leg having inner and outer surfaces and an outer mast front leg having
inner and outer surfaces, and a pair of U-shaped cross-sectional inner
masts each having an upper end and a lower end and slidably received
within the U-shape of respectively associated ones of said outer masts to
thereby provide with respect to each an inner mast front leg having an
outer surface cofacing said outer mast front leg inner surface of its said
associated outer mast and an inner mast rear leg having an outer surface
cofacing said outer mast rear leg inner surface of its said associated
outer mast, an outer mast roller mounted on said upper end of each said
outer mast in rolling engagement with said front leg outer surface of its
said associated inner mast, a rear liner attached to said outer mast rear
leg inner surface adjacent to said upper end of each said outer mast in
sliding engagement with said rear leg outer surface of its said associated
inner mast, an inner mast lower roller mounted on said lower end of said
inner masts in rolling engagement with one of said outer mast front leg
outer surface and said outer mast rear leg inner surface of its said
associated outer mast, the web of each said U-shaped outer mast providing
laterally facing, respectively opposite inner and outer side surfaces
thereof, and the web of each said U-shaped inner mast providing laterally
facing, respectively opposite inner and outer side surfaces thereof, and a
mast side roller mounted on said outer mast inner side surface adjacent to
said upper end of each said outer mast, each said mast side roller being
in rolling engagement with said outer side surface of its said associated
inner mast.
13. An upright assembly as claimed in claim 12, which further comprises a
side liner mounted on said inner mast outer side surface adjacent to said
lower end of each said inner mast, each said side liner being in sliding
engagement with said inner side surface of its said associated outer mast.
14. An upright assembly as claimed in claim 12, which further comprises an
inner mast side roller mounted on said inner mast outer side surface
adjacent to said lower end of each said inner mast, each said inner mast
side roller being in rolling engagement with said inner side surface of
its said associated outer mast.
Description
FIELD OF THE INVENTION
This invention relates to an upright assembly for a fork lift truck and,
more particularly, to an upright assembly in which a U-shaped
cross-sectional inner mast is received in a U-shaped cross-sectional outer
mast to be elevationally movable therein.
BACKGROUND OF THE INVENTION
Heretofore, as upright assemblies for fork lift trucks, there have been
known liner types in which an inner mast received in an outer mast is
elevationally guided by a liner, and roller types in which an inner mast
received in an outer mast is guided by rollers. Such upright assemblies of
the inner mast receiving type have the feature of a forward field of view
from the driver's seat greater than that of upright assemblies of the type
where an outer mast and an inner mast are aligned in the lateral direction
(right and left directions) of the fork lift truck.
FIG. 1 shows a conventional liner type upright assembly. In this upright
assembly, liners 5 are interposed between the front and rear inner faces
of an outer mast 1 and the front and rear outer faces of an inner mast 3
received in the outer mast 1, a side liner 7 is interposed between the
side inner face of the outer mast 1 and the side outer face of the inner
mast 3, and longitudinal and lateral moments acting on the inner mast 3
are supported by the liners 5, 7. A lift roller 11 attached to a lift
bracket 9 is made to roll in a space inside the inner mast 3.
However, conventional liner type upright assemblies have problems in that
sliding resistance between the masts 1 and 3 is large which adversely
affects the lifting speed of the mast, thereby reducing efficiency.
Further, the liners 5, 7 wear severely and it is hence necessary to
frequently replace the liners, a complicated task that increases
maintenance costs.
On the other hand, conventional roller type upright assemblies as disclosed
in Japanese Patent Publication No. 49-49548 and Japanese Utility Model
Laid Open No. 54-159575 are also known. FIGS. 2-4 show an upright assembly
equivalent to those disclosed in these official gazette documents. As
shown in the drawings, front and rear outer mast rollers 13 and 14 rolling
on the front and rear outer faces of the inner mast 3 are attached to the
upper end of the outer mast 1 through roller brackets 15, and small and
large inner mast rollers 17 and 18 rolling on the front and rear inner
faces of the outer mast 1 are attached to the lower end of the inner mast
3 through L-shaped roller brackets 19. Longitudinal moments are generated
by the mast rollers 13, 14 and 17, 18. In this case, forward moments
acting on the inner mast 3 are much larger than rearward moments, and the
inner mast roller 18 at the rear side has a larger diameter. As shown in
FIG. 2, lateral moments are supported by bringing the side face of the
rear inner mast roller 18 having a large diameter into contact with a
thick portion 1a formed at the inner corner of the outer mast 1. A lift
roller 11 attached to a lift bracket 9 is so received as to roll in the
inner space of the inner mast 3.
However, since the inner mast rollers 17 and 18 are disposed directly under
the inner mast 3 in this roller type upright assembly, the lift roller 11
at the lowermost portion of the lift bracket 9 when it is disposed at its
lowest position as shown in FIG. 3 must be at least the dimension D above
the rear inner mast roller 18. Particularly, since the roller pin 21 of
the inner mast roller 18 is only supported by one end on the L-shaped
roller bracket 19, the roller pin 21 needs to be strengthened by
increasing its diameter with the result that the diameter of the inner
mast roller 18 is unavoidably increased. Thus, the lift roller 11 on the
lift bracket 9 must be disposed at a considerably higher position than the
lower end of the roller bracket 19 which is substantially the lower end of
the inner mast 3, increasing the resultant overall height H of the upright
assembly, with the result that there are cases where such an assembly
cannot be used for loading/unloading in structures having low ceilings.
SUMMARY OF THE INVENTION
Accordingly, an object of this invention is to provide an improved upright
assembly for a fork lift truck in which sliding resistance between an
inner mast and an outer mast is minimized so that elevational movement of
the inner mast can be carried out smoothly.
Another object of this invention is to provide an upright assembly for a
fork lift truck in which the overall height thereof is made to be as low
as possible.
Still another object of the invention is to provide an upright assembly for
a fork lift truck in which a broad forward field Of view can be assured.
In order to achieve these and other objects, there is provided according to
this invention an upright assembly for a fork lift truck having a U-shaped
cross-sectional outer mast and a U-shaped cross-sectional inner mast
received in the outer mast, wherein an outer mast roller rollably
contacting the front outer face of the inner mast and a rear liner
slidably contacting the rear outer face of the inner mast are mounted at
the upper end of the outer mast, and an inner mast roller rollably
contacting front outer face of the outer mast and a front liner slidably
contacting the front inner face of the outer mast are mounted at the lower
end of the inner mast.
As the arrangement of the upright assembly described above is of the type
where the inner mast is received in the outer mast, a broad forward field
of view can be assured.
In such an upright assembly, large forward moments acting on the inner mast
are supported by the outer and inner mast rollers at the time of normal
loading/unloading operations, and relatively small rearward moments acting
at the time of traveling with an empty load are supported by the rear and
front liners. More specifically, since the elevational movements of the
inner mast at the time of loading/unloading are guided by the outer and
inner mast rollers, its sliding resistance is low and elevational
movements are smooth.
Further in relation to the fact that the inner mast roller is disposed at
the front side of the outer mast, it is possible to dispose the lift
roller of the lift bracket at the lower end of the inner mast when the
lift bracket is disposed at its lowermost position. Therefore, the overall
height of the upright assembly can be kept to a minimum as compared with a
conventional roller type upright assembly. Thus, loading/unloading
operations in structures having low ceilings becomes possible.
According to another embodiment of the present invention, there is provided
an upright assembly for a fork lift truck in which the inner mast roller
rollably contacting the rear inner face of the outer mast and the front
liner slidably contacting the front inner face of the outer mast are
mounted at the lower end of the inner mast. Further, in the upright
assembly, a roller bracket for supporting the roller pin of said inner
mast roller at both ends thereof is provided at the corner of the rear
lower end of the inner mast, and the roller bracket is formed in
substantially a triangular shape with the side opposing the lift roller on
the lift bracket rolling in the U-shaped space of the inner mast as an
oblique face.
With the arrangement of the upright assembly described above, similarly to
the first embodiment, large forward moments acting on the inner mast at
the time of normal loading/unloading operations are supported by the outer
and inner mast rollers.
Related to the fact that the roller pin is supported at both ends by the
roller bracket, the diameter of the roller pin of the inner mast roller
can be reduced to decrease the diameter of the roller. Further, since the
roller bracket, is formed substantially in a triangular shape with the
side of the roller bracket opposing the lift roller of the lift bracket as
the oblique face, the rising dimension from the lower end of the inner
mast can be kept short. As a result, the lift roller can be so disposed
that, when the lift bracket is at its lowermost position, it can approach
the lower end of the inner mast as much as possible.
These and other objects and features of the present invention will become
apparent from the following detailed description in conjunction with the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following detailed description, references will be made to the
attached drawings in which:
FIG. 1 is a cross-sectional view schematically showing a conventional liner
type upright assembly for a fork lift truck;
FIG. 2 is a cross-sectional view schematically showing a conventional
roller type upright assembly;
FIG. 3 is a cross-sectional view of a conventional upright assembly taken
along the line A--A of FIG. 2;
FIG. 4 is a perspective view showing the attaching structure of an inner
mast roller in a conventional roller type upright assembly;
FIG. 5 is a plan view schematically showing an upright assembly according
to an embodiment of the present invention with a cross-sectional view of a
lower portion of an upright assembly in a right half portion thereof;
FIG. 6 is a sectional view of an upright assembly taken along the line B--B
of FIG. 5, wherein a lift bracket is omitted;
FIG. 7 is a sectional view of an upright assembly taken along the line B--B
of FIG. 5, wherein the inner mast is disposed at its lowermost position;
FIG. 8 is an exploded perspective view showing the mounting structure of
the outer mast roller in the upright assembly of this invention;
FIG. 9 is an exploded perspective view showing the mounting structure of
the inner mast roller in the upright assembly of this invention;
FIGS. 10 and 11 are partial sectional views showing the mounting structure
of a liner and a side roller in the upright assembly of the invention;
FIG. 12 is a view schematically showing obstruction in the field of view
from a driver's seat according to the upright assembly of the invention;
FIG. 13 is a partial sectional view showing a modified embodiment of the
mounting structure of the liner;
FIG. 14 is a sectional view similar to FIG. 6 showing a modified embodiment
of the first embodiment of the invention;
FIG. 15 is a plan view schematically showing a second embodiment of a
upright assembly of this invention with a cross-sectional view of the
lower portion of the upright assembly in a right half portion thereof;
FIG. 16 is a sectional view of an upright assembly taken along the line
C--C of FIG. 15;
FIG. 17 is a sectional view of an upright assembly taken along the line
C--C of FIG. 15 with the view showing the state wherein the inner mast is
disposed at its lowermost position; and
FIG. 18 is a perspective view showing the mounting structure of the inner
mast roller in the upright assembly of the second embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 5-12, a pair of right and left outer masts 51 are
forwardly or rearwardly tiltably mounted at lower ends thereof to a truck
body (not shown) through mast supports 53, and are tilted forward or
rearward by tilt cylinders (not shown) coupled to tilt brackets 55 at
substantially intermediate portions of the outer masts 51. The right and
left outer masts 51 are formed in U-shaped cross section, and right and
left inner masts 57 formed in U-shaped cross section are elevationally
movably received in the inner spaces of the outer masts 51, respectively.
Outer mast rollers 59 rolling on the front outer faces of the inner masts
57 are attached to the front sides of the upper ends of the outer masts 51
through roller brackets 61. Inner mast rollers 63 rolling on the front
outer faces of the outer masts 51 are attached to the front sides of the
lower ends of the inner masts 57 through roller brackets 65, and forward
(in a direction of arrow F in FIG. 6) moments acting on the inner masts 57
are supported by both the rollers 59 and 63.
As shown in FIG. 8, the roller bracket 61 for the outer mast roller 59 is
composed of a combination of a stationary bracket 61a fixed by welding or
the like to the front face of the outer mast 51 to protrude forwardly, and
a protective bracket 61b clamped by bolts 67 to the stationary bracket
61a. The outer mast roller 59 is disposed in a containing recess 69 formed
in the protective bracket 61b such that the front and rear portions
thereof are exposed, and rotatably associated with a roller pin 71 fixed
through the roller bracket 61 through a radial bearing 73 and a pair of
right and left thrust bearings 75.
As shown in FIG. 9, the roller bracket 65 for the inner mast roller 63 is
composed of a combination of a stationary bracket 65a fixed by welding or
the like to the front edge face of the inner mast 57 to protrude
forwardly, and a protective bracket 65b coupled by bolts 77 to the
stationary bracket 65a. The inner mast roller 63 is disposed in a
containing recess 79 formed in the protective bracket 65b such that the
front and rear portions thereof are exposed, and rotatably associated with
a roller pin 81 fixed through the bracket 65 through a radial bearing 83
and a pair of right and left thrust bearings 85.
With the arrangement described above, the outer mast roller 59 and the
inner mast roller 63 are protected against dropping articles or the like.
Since the roller pins 71 and 81 are supported at..both ends thereof by the
roller brackets 61b and 65b, respectively, the pins are reduced in
diameter, and the rollers are hence decreased in diameter, thereby
reducing the forward protrusion thereof.
A rear liner 87 slidably contacting the rear outer face of the inner mast
57 is disposed on the rear inner face of the upper end of the outer mast
51, while a front liner 89 slidably contacting the front inner face of the
outer mast 51 is disposed on the front outer face of the lower end of the
inner mast 57, and rearward (in the direction of arrow R in FIG. 6)
moments acting on the inner mast 57 are supported by both the front and
rear liners 87 and 89. Generally, rearward moments acting on the inner
mast 57 are generated at the time of traveling with an empty load, and are
small in magnitude. Accordingly, a supporting structure with the liners 87
and 89 provides sufficient strength.
A mast side roller 91 rolling on the outer laterally facing surface of the
web of the inner mast 57 is mounted on the side of the upper end of the
outer mast 51, while a side liner 93 sliding on the inner laterally facing
surface of the web of the outer mast 51 is mounted on the inner laterally
facing surface of the web adjacent to the lower end of the inner mast 57,
and rightward and leftward moments are supported by the mast side roller
91 and the side liner 93.
As shown in FIGS. 10 and 11, the liners 81, 87 and 93 are attached by
engaging upper and lower pins 95 provided on the respective liners with
holes 97 formed in the masts 51 an 57. The mast side roller 91 is in
rolling contact with the outer face of the side of the inner mast 57
through an opening 99 perforated through the outer mast 51 as shown in
FIG. 11, and attached to the outer mast 51 through a bracket 101. As shown
in FIG. 13, the sliding face of the outer mast 51 on which the side liner
93 of the inner mast 57 slides may be formed on the raised portion 51c of
the outer mast 51. Forming such a raised portion is advantageous in that
it facilitates machining for improving the smoothness of the sliding face.
As shown in FIG. 5, lift cylinders 103 stand at the rear of the outer masts
51 and are supported at the lower ends thereof on the outer masts 51 by
the lower cross beam 51a of the outer mast 51 through a bracket (not
shown), the upper end of the piston rod 105 being coupled to the upper tie
beam 57a of the inner mast 57.
As shown in FIG. 5, the upper tie beam 57a is so extended as to be
introduced to the side of the outer mast 51, and a chainwheel 107 is
mounted on the extended portion with the rotating axis thereof lateral
thereto. A lift chain 109 engaged with the chainwheel 107 is coupled so
that the rear side thereof passes around the outside of the chainwheel 107
to a chain support (not shown) protruding on the outer face of the upper
portion of the outer mast 51, and the front side passes the front side of
the chainwheel 107 to be coupled on a chain support 115 of a lift bracket
113 for supporting a fork 111. More specifically, the front side coupled
on the lift bracket 113 so is disposed as to utilize the projecting plane
of the outer mast 51 in the longitudinal direction thereof. The lift
bracket 113 is elevationally moved upwardly or downwardly through lift
rollers 117 rotatably disposed in the inner space of the inner mast 57. In
FIG. 5, symbol 51b denotes the upper cross beam of the outer mast 51, and
symbol 57b denotes the lower tie beam of the inner mast 57.
In the upright assembly described above, since the inner mast 57 which
obstructs the forward field of view is received in the outer mast 51 and
the lift cylinder 103 is also disposed to the rear of the outer mast 51,
and further since the front side of the lift chain 109 connected to the
lift bracket 113 is disposed on the forward portion of the outside of the
mast 51 in a plane projecting from the outer mast 51 in a longitudinal
direction thereof, the zone of the forward field of view that is
obstructed by the front sides of the inner mast 57, the lift cylinder 103
and the lift chain 109 is narrowed as designated by the shaded portions in
FIG. 12, so that a wide forward field of view can be obtained.
Since large forward moments designated by arrow F in FIG. 6 acting on the
inner mast 57 by weights (the weight when a load is carried on the fork
lift truck) on the bracket 113 or the forks 111 are supported by the outer
mast roller 59 and the inner mast roller 63 in a normal loading work mode,
the inner mast 57 can be smoothly elevationally moved with small sliding
resistance.
With the arrangement described above, the inner mast roller 63 rolls on the
outer face of the front side of the outer mast 51, i.e., a construction
wherein it is disposed on the outside of the outer mast 51. Thus, the lift
roller 117 on the lowermost portion of the lift bracket 113 can be
disposed so as to move to the lower end of the inner mast 57. Accordingly,
the upright assembly according to the present invention can utilize the
entire length of the inner mast 57 as the effective rolling zone of the
lift roller 117 different from conventional roller type upright assemblies
wherein the inner mast roller is disposed at the lower end of the inner
mast. Therefore, the entire height Hl of the upright assembly can be kept
to a lower value.
FIG. 14 shows a modified embodiment of the present invention described
above. This modified embodiment is the same as the above-described
embodiment in arrangement except that a mast side roller 119 is provided
on the side face of the outer mast 51 instead of the side liner 93 of the
upright assembly of the first embodiment described above and a
longitudinal plate 121 having a protrusion jutting forward to the same
extent as that of the inner mast 57 is provided on the front face of the
outer mast 51. In other words, the plate 121 protrudes forwardly to
substantially the same extent as does the inner mast roller 63 mounted on
the lower end of the inner mast 57, as shown in FIG. 14.
Therefore, in this modified embodiment, lateral moments from eccentric
loads acting on the inner mast 57 when loading freight are supported by
the mast side roller 91 of the outer mast 51 and the mast side roller 119
of the inner mast 57. Thus, the sliding resistance of the inner mast 57
when elevating up or down can be further effectively reduced. Also, since
the closest that the outer mast 51 can come to the rear deck T of a truck
can be restricted by the plate 121 of the outer mast 51 when loading or
unloading the truck as designated by the imaginary lines in the drawing,
interference of the inner mast roller 63 with the gate t of the rear deck
T is avoided where the outer mast 51 approaches the rear deck T, thereby
preventing damage to the gate t or the inner mast roller 63 beforehand
Though not shown, the side mast roller 119 of the inner mast 57 shown in
FIG. 14, and the side liner 93 of the first embodiment may be provided
together, so that lateral moments may be supported by the side roller 91
of the outer mast 51 and the side liner 93 of the inner mast 57 when the
inner mast 57 is down resulting in the overlap area of the inner mast 57
and the outer mast 51 being large. When the inner mast 57 is up resulting
in a small overlap area, lateral moments may be supported by the mast side
roller 91 of the outer mast 51 and the mast side roller 119 of the inner
mast 57.
Referring to FIGS. 15-18, a second embodiment of the present invention will
next be described. The second embodiment differs from the first embodiment
in the mounting state of the inner mast roller, but the other portions
thereof are substantially the same, wherein the same reference numerals as
those in the first embodiment denote the same or equivalent components,
and descriptions thereof will be omitted.
As shown in the drawing, an inner roller 201 is mounted by a roller bracket
203 to the lower end of the inner mast 57 so as to roll on the inner face
of the rear side of the outer mast 51. As best shown in FIG. 18, the
roller bracket 203 for the inner mast roller 201 is fixed by welding or
the like to the corner of the lower end of the rear side of the inner mast
57. The roller bracket 203 is formed substantially in a U-shape in a
horizontal plane, and substantially in a triangular shape in a side plane,
and the front face thereof opposite the lift roller 117 of the lowermost
portion of the lift bracket 113 is oblique. The inner mast roller 201 is
disposed in the inner space of the roller bracket 203, and rotatably
mounted at both ends there of by roller pins 205 supported to the roller
brackets 203.
Large forward moments designated by an arrow F in FIG. 16 act on the inner
mast 57, and these moments are supported by the outer mast roller 59
rolling on the outer face of the front side of the inner mast 57 and the
inner mast roller 201 rolling on the inner face of the rear side of the
outer mast 51.
In the second embodiment described above, the roller pin 205 of the inner
mast roller 201 is supported, similarly to the first embodiment, at both
ends thereof by the roller bracket 203. Thus, the pin can be reduced in
diameter, and the roller can hence be decreased in diameter. In addition,
since the roller bracket 203 itself is formed substantially in the
triangular shape with the front side being oblique, the rising size from
the lower end of the inner mast 57, i.e., the range of interference with
the lift roller 117 can be reduced. Therefore, as shown in FIG. 17, a
distance L between axes of the inner mast roller 201 and the lift roller
117 when the lift bracket 113 is disposed at the lowermost position can be
considerably decreased. As a result, the entire height H2 of the upright
assembly can be kept to a lower value as compared with that of
conventional roller type upright assemblies.
It is thought that the present invention and many of its attendant
advantages will be understood from the foregoing description and it will
be apparent that various changes may be made in the form, construction and
arrangement thereof without departing from the spirit and scope of the
invention or sacrificing all of its material advantages, the form
hereinbefore described being merely preferred or exemplary embodiments
thereof.
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